Circulating air by using aesthetically pleasing design fan blades has been done for many years. Leaf shaped flat type blades have become popular in recent years. See for example, U.S. patents: U.S. Pat. No. D387,156 to Johnson; U.S. Pat. No. D443,352 and U.S. Pat. No. D454,636 to Lantz; U.S. Pat. No. D485,345 and U.S. Pat. No. D510,992 to Bucher; U.S. Pat. No. D491,657 and U.S. Pat. No. 6,890,155 to Cartwright; and U.S. Pat. No. 6,923,624 to Tsai. Another popular blade style over the years is a flat planar rectangular blade that can have a slight tilt, as shown for example in U.S. patents: U.S. Pat. No. Des. 355,027 to Young and U.S. Pat. No. Des. 382,636 to Yang. These patents while moving air are not concerned with maximizing optimum downward airflow.
Furthermore, many of the flat ceiling fan blades have problems such as poor performance at high speeds, wobbling, and excessive noise that is noticeable to persons in the vicinity of the fan blades.
Also, the older design prior art leaf shaped ceiling fan blades are more prone to wobble and noise as the lift produced is non-uniform across the length of the blades.
Aircraft, marine and automobile engine propeller type blades have been altered over the years to shapes other than flat rectangular. See for example, U.S. Pat. No. 1,903,823 to Lougheed; U.S. Pat. No. 1,942,688 to Davis; U.S. Pat. No. 2,283,956 to Smith; U.S. Pat. No. 2,345,047 to Houghton; U.S. Pat. No. 2,450,440 to Mills; U.S. Pat. No. 4,197,057 to Hayashi; U.S. Pat. No. 4,325,675 to Gallot et al.; U.S. Pat. No. 4,411,598 to Okada; U.S. Pat. No. 4,416,434 to Thibert; U.S. Pat. No. 4,730,985 to Rothman et al. U.S. Pat. No. 4,794,633 to Hickey; U.S. Pat. No. 4,844,698 to Gornstein; U.S. Pat. No. 5,114,313 to Vorus; and U.S. Pat. No. 5,253,979 to Fradenburgh et al.; Australian Patent 19,987 to Eather. However, these patents are describing devices that are generally used for high speed water, aircraft, and automobile applications where the propellers are run at high revolutions per minute(rpm) generally in excess of 500 rpm. None of these propellers are designed for optimum airflow at low speeds of less than approximately 200 rpm which is the desired speeds used in overhead ceiling fan systems.
Some alternative blade shapes have been proposed for other types of fans. See for example, U.S. Pat. No. 1,506,937 to Miller; U.S. Pat. No. 2,682,925 to Wosik; U.S. Pat. No. 4,892,460 to Volk; U.S. Pat. No. 5,244,349 to Wang; Great Britain Patent 676,406 to Spencer; and PCT Application No. WO 92/07192.
Miller '937 requires that their blades have root “lips 26” FIG. 1 that overlap one another, and would not be practical or useable for three or more fan blade operation for a ceiling fan. Wosik '925 describes “fan blades . . . particularly adapted to fan blades on top of cooling towers such for example as are used in oil refineries and in other industries . . . ”, column 1, lines 1-5, and does not describe any use for ceiling fan applications. The Volk '460 patent by claiming to be “aerodynamically designed” requires one curved piece to be attached at one end to a conventional planar rectangular blade. Using two pieces for each blade adds extreme costs in both the manufacturing and assembly of the ceiling itself. Furthermore, the grooved connection point in the Volk devices would appear to be susceptible to separating and causing a hazard to anyone or any property beneath the ceiling fan itself. Such an added device also has necessarily less than optimal aerodynamic properties.
Tilted type design blades have also been proposed over the years. See for example, U.S. Pat. No. D451,997 to Schwartz.
However, none of the prior art modifies design shaped blades to optimize twist angles to optimize energy consumption and airflow, and reduce wobble and noise problems
Thus, the need exists for better performing leaf shaped ceiling fan blades over the prior art.